Ipk is file extension for most the enigma2 plugins files and composed of compressed data of the plugin distributed in different folders for automatic installation,Barry allen and drivers are other examples of ipk files
There are three common methods for installation of ipk files

1- Telnet command by using Telnet from windows and better from DCC program

Transfer your ipk file to dreambox /tmp folder by dcc-ftp commands and put the following command in telnet window
Code:
ipkg install /tmp/enigma2-plugin-extensions-pluginame.ipk
you can use copy-paste to put ipk filename
some images like newnigma and openpli do not accept ipkg command we can use opkg instead
The following is demonstration of Barry allen ipk file installation by this method

2- DCC-upload packages method
This is the easiest installation method specially for beginner

3-Manual installation
after copy the ipk file to dreambox .tmp folder from dreambox we follow the demonstration(this is for old gemini but same principal apply to all images)